One-Step Fabrication of Multifunctional Core-Shell Nanofibres by Co-Electrospinning

A.L. Medina-Castillo, J. F. Fernandez-Sanchez, A. Fernandez-Gutierrez

NANOSPAIN 2012 Nanosensors for industrial applications

February 27,2012 Santander (Spain)

Universidad

de Granada

Universidad

de Granada

Introduction

Optical sensors for O2 and pH

Incorporation of magnetic properties

Three functionalities in one-step synthesis: our proposal

Experimental

Shell: pH-sensitive polymer

Core: magnetic and O2-sensitive

Synthesis of magnetic, pH and O2-sensitive tissues

Analytical properties

Conclusions

Acknowledges

Overview

Introduction

Optical sensors for pH and O2

Data dye

pH determination: change in absorption or emission of light

0.0

0.4

0.8

1.2

1.6

450 550 650 750

Wavelength (nm)

Abso

rban

ce

D-

DH

Introduction

Data dye

O2 determination: luminescence quenching

Presence of O2

Absence of O2

I/I0 [O2]

Optical sensors for pH and O2

Introduction

Incorporation of magnetic properties

The incorporation of magnetic properties into the sensing material allows the in situ formation of sensor spots by magnet separation and optical readout from the outside or an easy way to fix the sensing material at the tip of an optical fiber.

Introduction

Incorporation of magnetic properties

Mag-NP

Sensitive to O2

Introduction

Our proposal

Magnetic Sensitive

to pH

+ +

Core (hydrophobic):

Magnetic Sensitive to O2

Shell (hydrophilic):

Sensitive to pH

For the successful conjugation of these three functionalities, two different chemical environments on the same material are necessary: a hydrophilic environment for the pH indicator and a hydrophobic environment for the O2 indicator. The magnetic susceptibility could be incorporated in either of these environments.

Core (hydrophobic):

Magnetic Sensitive to O2

SShell (hydrophilic):

Introduction

Our proposal

Sensitive to pH

Magnetic nanoparticles O2-sensitive dye Polymer

pH-sensitive polymer

Co-electrospinning technique allows a strict control of the process and thus the design of well-organized multifunctional materials; thus by one-step fabrication different pairs of copolymers can be processed as coaxial micro- and nano-fibres .

Universidad

de Granada

Universidad

de Granada

Introduction

Optical sensors for O2 and pH

Incorporation of magnetic properties

Three functionalities in one-step synthesis: our proposal

Experimental

Shell: pH-sensitive polymer

Core: magnetic and O2-sensitive

Synthesis of magnetic, pH and O2-sensitive tissues

Analytical properties

Conclusions

Acknowledges

Overview

Lineal copolymer with a pH-sensitive fluorescent probe covalently attached. It should be water-insoluble and soluble in polar organic solvents. These copolymers are based on the copolymerization of FOA, MMA and HEMA (poly FOA-co-MMA-co-HEMA) by reverse ATRP. In addition, MAPTAC or AAMPs can be added to change slightly the charge and therefore the pKa.

Experimental

Shell: pH-sensitive polymer

J. Mater. Chem., 2011, 21, 6742

NP1 NP1(X) NP1(-)A

pKa= 8.5 pKa= 7.5 pKa= 9.6

nm

x

Experimental

Shell: pH-sensitive polymer

J. Mater. Chem., 2011, 21, 6742

NP1(X)

pKa= 7.5 Mw=104517 Dalton Mw/Mn: 1.4 Intrinsic Viscosity: 0.28 dL/g

pH-sensitive nanofibres mats

Experimental

Shell: pH-sensitive polymer

J. Mater. Chem., 2011, 21, 6742

Collector

Fibers

Syringe

Polymer solution

Injector voltage: 16.4 kV

Collector voltage: -9.7 kV

Dis

tan

ce: 2

9.5

cm

30 wt% NP1(X) 1.75 wt% HCl DMF Conductivity: 678 S/cm

2.5 h to collect 20 cm diameter

169±24 nm diameter

Spinning nozzle (Φext/int=1.5/1.1 mm)

High voltage for injection

High voltage for collection

-11 -9 -7 -5 -3 -1 1

0

200

400

600

800

6 7 8 9 10 11

pH

Rel

ati

ve

Flu

ore

scen

ce I

nte

nsi

ty (

a.u

.)

R2 = 0.998

pKa = 7.85 ± 0.030

I0 = 758.71 ± 10.38

B =18.87 ± 7.53

pH-sensitive nanofibres mats

Experimental

Shell: pH-sensitive polymer

1 µm

20 cm

20 µm

J. Mater. Chem., 2011, 21, 6742

To incorporate oxygen-sensitive properties it is necessary to immobilize a O2-sensitive complex. These kind of complexes are hydrophobic.

Experimental

Core: Magnetic and O2-sensitive

PtOEP

Polymer

Magnetic particles

PMMA

γ-Fe3O4-OA

It decants in few minutes

Solvent

THF

Adv. Funct. Mater., 2011, 21, 3844

Experimental

Core: Magnetic and O2-sensitive

To increase the stability of γ-Fe3O4-OA in PMMA/THF, we used γ-Fe3O4-OA encapsulated into MMA-co-EDMA

120 nm

MMA-co-EDMA magNP particles

MMA-co-EDMA matrix is chemically similar to PMMA and thus the chemical affinity between them is maximized.

Adv. Funct. Mater., 2011, 21, 3844

To incorporate oxygen-sensitive properties it is necessary to immobilize a O2-sensitive complex. These kind of complexes are hydrophobic.

Experimental

Core: Magnetic and O2-sensitive

PtOEP

Polymer

Magnetic particles

PMMA

Solvent

THF

Adv. Funct. Mater., 2011, 21, 3844

120 nm

MMA-co-EDMA They provide a highly stable inner suspension which allows a coaxial cone in steady state for a long time (more than 4 h).

Experimental

Synthesis of magnetic, pH and O2-sensitive tissues

Adv. Funct. Mater., 2011, 21, 3844 Collector

Core-Shell Fibers

Coaxial tube

Outer polymer solution

High voltage for injection

Injector voltage: 9.7 kV

Collector voltage: - 0.7 kV

Dis

tan

ce: 2

3.5

cm

28.2wt% NP1(X) 1.4 wt% PVP (Mw: 1,300,000) 70.4 wt% DMF

Inner polymer solution

12.7 wt% PMMA 0.2 wt% PtOEP 2.5 wt% magNP 84.7 wt% THF

High voltage for collection

Flow-rate 1.0 mL/h

Flow-rate 0.5 mL/h

External tube (Φext/int=1.7/1.4 mm)

Internal tube (Φext/int=1.0/0.7 mm)

Experimental

Synthesis of magnetic, pH and O2-sensitive tissues

Adv. Funct. Mater., 2011, 21, 3844

Effect of composition: amount of mag-NP

Outer polymer solution

28.2wt% NP1(X) 1.4 wt% PVP (Mw: 1,300,000) 70.4 wt% DMF

Inner polymer solution

13.3 wt% PMMA 0.0 wt% PtOEP 0.6 wt% magNP 84.7 wt% THF

Outer polymer solution

28.2wt% NP1(X) 1.4 wt% PVP (Mw: 1,300,000) 70.4 wt% DMF

Inner polymer solution

12.7 wt% PMMA 0.0 wt% PtOEP 2.5 wt% magNP 84.7 wt% THF

C1

C2

Experimental

Synthesis of magnetic, pH and O2-sensitive tissues

Adv. Funct. Mater., 2011, 21, 3844

Effect of composition: incorporation of PtOEP

Outer polymer solution

28.2wt% NP1(X) 1.4 wt% PVP (Mw: 1,300,000) 70.4 wt% DMF

12.7 wt% PMMA 0.0 wt% PtOEP 2.5 wt% magNP 84.7 wt% THF

C2

C2-O2

Inner polymer solution

Outer polymer solution

28.2wt% NP1(X) 1.4 wt% PVP (Mw: 1,300,000) 70.4 wt% DMF

12.7 wt% PMMA 0.2 wt% PtOEP 2.5 wt% magNP 84.7 wt% THF

Inner polymer solution

Experimental

Synthesis of magnetic, pH and O2-sensitive tissues

Adv. Funct. Mater., 2011, 21, 3844

Effect of composition: incorporation of PtOEP

Outer polymer solution

28.2wt% NP1(X) 1.4 wt% PVP (Mw: 1,300,000) 70.4 wt% DMF

12.7 wt% PMMA 0.0 wt% PtOEP 2.5 wt% magNP 84.7 wt% THF

C2

C2-O2

Inner polymer solution

Outer polymer solution

28.2wt% NP1(X) 1.4 wt% PVP (Mw: 1,300,000) 70.4 wt% DMF

12.7 wt% PMMA 0.2 wt% PtOEP 2.5 wt% magNP 84.7 wt% THF

Inner polymer solution

0.0

0.2

0.4

0.6

0.8

1.0

1.2

1.4

1.6

1.8

0.0E+00 1.0E+04 2.0E+04 3.0E+04 4.0E+04 5.0E+04

Applied magnetic f ield (Oe)

Magnetiz

atio

n (

em

u/g

)

C2

C2-O2

C1

Experimental

Synthesis of magnetic, pH and O2-sensitive tissues

Adv. Funct. Mater., 2011, 21, 3844

Distribution of NP1(X) and PtOEP

Adv. Funct. Mater., 2011, 21, 3844 λexc= 488 nm

C2-O2 λexc= 488 nm λ'exc= 530nm

pH calibration and reversibility

Experimental

Analytical properties

500

550

600

650

700

750

800

850

900

0.5 5.5 10.5 15.5 20.5 25.5 30.5

t (mim)

Lum

inis

cence in

t. (a

.u.)

pH=6

pH=7

pH=8

Effect of pH on the determination of O2

Experimental

Analytical properties

0

100

200

300

400

500

600

1

lum

inis

cence int.

(a

.u.)

0% O2

10% O2

20% O2

100% O2

0% O2

10% O2

20% O2

100% O2

0% O2

10% O2

20% O2

100% O2

pH=6 pH=7 pH=8

Stern-Volmer plot in gas phase

Experimental

Analytical properties

y = 3.8792x + 0.9387

R2 = 0.9931

1.0

1.5

2.0

2.5

3.0

0.0 0.1 0.2 0.3 0.4 0.5

pO2 (bar)I 0

/I

0

200

400

600

800

1000

0 5 10 15 20 25 30 35 40 45

Time (min)

Lu

min

esc

en

ce i

nt.

(a.u

.)

0%

O2

5%

O2

10%

O2

20%

O2

30%

O2

40

% O

2

50%

O2

100%

O2

5%

O2

10%

O2

20%

O2

30%

O2

40

% O

2

50%

O2

0%

O2

Ksv= 3.88 bar-1 t90 (0-5%) = 15 s t90 (5-0%) = 12 s

0

150

300

450

600

750

900

0 10 20 30 40

Time (min)

Lu

min

esc

en

ce i

nt.

(a.u

.)

y = 7.0659x + 0.9155

R2 = 0.9963

1

2

3

4

5

0.0 0.1 0.2 0.3 0.4 0.5

pO2 (bar)I 0

/I

0%

O2

5%

O2

10%

O2

20%

O2

30%

O2

40%

O2

50%

O2

100%

O2

5%

O2

10%

O2

20%

O2

30%

O2

40%

O2

50%

O2

0%

O2

Stern-Volmer plot in solution

Experimental

Analytical properties

Ksv= 7.07 bar-1 t90 (0-5%) = 15 s t90 (5-0%) = 12 s

•Novel lineal, pH-sensitive, water insoluble copolymers have been

synthesized.

•Co-electrospinning is a powerful tool to design multifunctional core-shell

fibres with controlled distributions of axial anisotropies in composition

with high production and cost effectiveness.

•The new, advanced multifunctional material are magnetic and have a well-

organised structure which allows the optical monitoring of pH and O2, in

situ, at real time and simultaneously.

•The magnetic susceptibility of the core-shell fibres can be tuned by

changing the percentage of mag-NP particle in the inner suspension.

Conclusions

Conclusions

Acknowledgment

Nanotechnology and Sensors research line of FQM-297

www.ugr.es/local/fqm297

Financial support:

R&D Department Nanomateriales y Polímeros S.L.

www.nanomyp.com